Developing a novel sensor based on ionic liquid molecularly imprinted polymer/gold nanoparticles/graphene oxide for the selective determination of an anti-cancer drug imiquimod.

Despite its useful properties, imiquimod (IMQ), known as an anti-cancer drug, can be harmful to the skin at high concentrations. Therefore, we have developed a novel electrochemical sensor to determine IMQ, for the first time. A glassy carbon electrode (GCE) was modified by a new composite comprising of ionic liquid-based molecularly imprinted polymer (MIP) and gold nanoparticles/graphene oxide (Au/GO). The MIP/Au/GO nanocomposite was synthesized through non-covalent imprinting process in the presence of IMQ, as template molecule and characterized by SEM and FT-IR. The square wave voltammetry technique (SWV) was applied for IMQ determination in 0.1 M phosphate buffer solution (PBS) at pH 7.0. Several parameters affecting the IMQ quantification were evaluated and optimized. Under the optimized conditions, the sensor presented a linear range of 0.02-20.0 µM, a limit of quantification and detection of 0.02 µM and 0.006 µM, respectively. Low RSD values indicate the good repeatability and reproducibility of the modified electrodes in preparation and determination procedures. The satisfactory results indicated that the proposed sensor could be successfully applied for IMQ determination in real samples.

Decoration of graphene oxide with NiO@polypyrrole core-shell nanoparticles for the sensitive and selective electrochemical determination of piceatannol in grape skin and urine samples.

For the first time, we developed an electrochemical sensor for piceatannol based on a new type of nanocomposite: graphene oxide nano sheets decorated with core-shell NiO@polypyrrole nanoparticles (NiO@Ppy/GO) mixed with nafion and casted on the surface of glassy carbon electrode. The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) techniques. The square wave voltammetry as a sensitive technique and cyclic voltammetry were selected for the quantification of piceatannol in 0.1 M phosphate buffer solution (pH 7.0). Several parameters were evaluated such as pH value, scan rate and supporting electrolyte type for the determination of piceatannol. In addition, selectivity and repeatability measurements were also evaluated. Under the optimized conditions, linear range and limit of detection were obtained 0.01-10.0 µM and 0.003 µM, respectively. Relative standard deviation for 3.0 µM and 6.5 µM were calculated 3.25% and 1.83%, respectively. The proposed sensor was applied successfully for the quantification analysis of piceatannol in grape skin essential oil and urine sample with satisfactory results.

Electrospun composite nanofibers of poly vinyl pyrrolidone and zinc oxide nanoparticles modified carbon paste electrode for electrochemical detection of curcumin.

A simple and novel ferrocene-nanofiber carbon paste electrode was developed to determine curcumin in a phosphate buffer solution at pH=8. ZnO nanoparticles were produced via a sonochemical process and composite nanofibers of PVP/ZnO were prepared by electrospinning. The characterization was performed by SEM, XRD and IR. The results suggest that the electrospun composite nanofibers having a large surface area promote electron transfer for the oxidation of curcumin and hence the FCNFCPE exhibits high electrocatalytic activity and performs well in regard to the oxidation of curcumin. The proposed method was successfully applied for measurement of curcumin in urine and turmeric as real samples.